Investigation of the density turbulence in ohmic ASDEX plasmas

A 119 μm homodyne laser scattering experiment is used on ASDEX to investigate wavenumber and frequency of the density fluctuations occuring in the different operational conditions of the machine. The changes of the density turbulence caused by additional heating are of primary interest with regard to a possible correlation to anomalous transport. Therefore, in the current experiment particular emphasis is placed on these investigations. On the other hand it is the ohmic phase which constitutes the least complicated physical situation in a tokamak and is therefore best suited to reveal the basic physical nature of the density turbulence. In the following we present a summary of our findings in the ohmic phase and make an attempt to compare these findings with what would be expected from the simplest model of density-gradient-driven driftwave turbulence saturated at the mixing-length level. (author) 3 refs., 4 figs